The invention relates to a control system for controlling the operation of a power take-off (PTO) shaft control device and, if applicable, other control devices of a utility vehicle. The control system includes a control unit that is electrically connected to the control devices, to switch s or switches for the manual control of the control devices and to an automatic mode switch to activate or deactivate an automatic mode for the automatic control of the control devices. In response to signals from a hitch switch, the control system transmits control signals for raising and lowering an attached implement hitch. The control unit automatically disengages the PTO shaft when the automatic mode is activated, as long as a pre-set hitch position is exceeded upon raising the attached implement hitch.
Such a control system is shown in U.S. Pat. No. 5,558,163, issued Sep. 24 1996 and assigned to the assignee of this application (Atty. Docket No. 8678). In this control system a number of switch controlled operations, such as PTO shafts, differential lock and all-wheel drive, are controlled in an automatic sequence depending upon the position of the hitch. When an automatic mode is activated, the operations are disengaged according to a pre-set program when the hitch is raised, and re-engaged when the hitch is lowered. Thus, during the preparation for a turn, the number of manual operations can be reduced considerably. For safety reasons the PTO shaft, however, is not automatically re-engaged during hitch lowering. Rather, the PTO shaft is re-engaged manually with a PTO shaft switch. Finding the correct point in time for the engagement of the PTO shaft requires concentration and skill on the part of the operator. Too early engagement can overload or damage the PTO shaft and the attached transmitting linkage, since at that point the implement is raised out of the ground considerably and the PTO shaft connection is angled sharply. Furthermore, when the PTO shaft is rotating the fully raised implement can eject dirt particles that can be dangerous. If the PTO shaft is engaged too late, the implement is already in contact with the ground or the plants that are to be worked. This makes difficult or prevents the running of the PTO shaft.